1. Field of the Invention
This invention pertains generally to magnetic resonance imaging, and more particularly to high spatial and temporal resolution dynamic contrast-enhanced magnetic resonance angiography or imaging using compressed sensing with magnitude image subtraction.
2. Description of Related Art
High-resolution 3D contrast-enhanced magnetic resonance angiography (CE-MRA) has emerged as a widely accepted and powerful technique for the diagnostic assessment of almost all vascular networks. Its non-invasive nature, lack of ionizing radiation and the safety of gadolinium-based contrast agents make CE-MRA an appealing alternative to digital subtraction angiography (DSA) and computed tomography angiography (CTA). Furthermore, dynamic (time-resolved) CE-MRA provides simplified scanning logistics and improved evaluation of the hemodynamic consequences of complex vascular anatomy and pathologies while avoiding some of the limitations of traditional single-phase CE-MRA, such as incorrect contrast bolus timing and venous contamination.
Dynamic CE-MRI is also used for qualitative and quantitative assessment of tissue perfusion in various oncological applications. However, due to limitations in image acquisition speed, it is difficult to achieve high temporal and spatial resolution at the same time. As a result, typical dynamic CE-MRA acquisitions have lower spatial resolution than found with conventional CE-MRA.
The conventional clinical set-up allows the acquisition of a chest CE-MRA with 1.1×0.9×1.2 mm3 spatial resolution within a 24 second breath-hold. However, the 24 sec temporal resolution does not provide adequate speed for capturing the hemodynamics of a rapidly changing vascular bed. Therefore, high resolution CE-MRA is normally preceded by a separate dynamic CE-MRA sequence such as (TWIST) using a very small contrast bolus. To obtain an apparent temporal window less than 5 sec, the sequence sacrifices through-plane spatial resolution (1×1×6 mm3) and uses a view-sharing technique whereby the k-space center is updated more frequently than the periphery and in turn the under-sampled periphery is shared among neighboring frames. As a result, the temporal footprint of each image frame, which is approximately 10 seconds, results in temporal blurring of rapidly changing events.
Accordingly, there is a need for a dynamic CE-MRA acquisition and image reconstruction strategy that can provide a true temporal resolution higher than TWIST and can acquire high spatial resolution CE-MRA in a shorter time window than is currently possible. The present invention satisfies that need as well as others and is generally an advancement in the art.